This invention relates to a vibrating coil assembly for use in mirror galvanometers, light-beam oscillographs and the like having a moving coil suspended between two tension wires or ribbons, and a mirror. Such vibrating coil assemblies are used, for example, in light-beam oscillographs. There, the taut ribbons are fastened directly to the moving coil so that the tension they exert is transmitted directly to the moving coil. This brings about the danger of deforming the moving coil, which can lead to a degradation of the measuring properties of the vibrating coil assembly.
A vibrating coil assembly is described in German Pat. No. 2,508,055 in which the transmission of the tension force to the moving coil proper is avoided by the use of a support member for the moving coil, the ends of which are engaged by the taut wires. (German Pat. No. 2,508,055). This support member, which can consist, for instance, of a tube, and which has depressions transverse to the direction of rotation of the vibrating coil assembly, increases the inertial mass of the vibrating structure. Further, a weight distribution which is asymmetrical to the axis of rotation results, also leading to an increase in the moment of inertia. Overall, these effects serve to reduce the measuring sensitivity of the vibrating coil assembly. The depressions in the support members also result in an enlarged dimension of the vibrating coil assembly in a direction perpendicular to the axis of rotation and so require a larger total space.
German Pat. No. 2,242,957 discloses a vibrating coil assembly in which the moving coil is fastened at an angle to, and penetrated by, a single tension wire or a ribbon; here, too, no tension forces become effective at the moving coil. Because the position of the moving coil is asymmetrical to the axis of rotation, however, more space is, again, required and lower measuring sensitivity results.
It is an object of this invention to provide a vibrating coil assembly of the type mentioned above which, like the known vibrating coil assemblies with tensionrelieved moving coils, is easy to install, but which requires less space and has a higher measuring sensitivity.